Heretofore, in processes for the production of semiconductor devices, for example, IC or LSI, microfabrication has been conducted by means of lithography using a resist composition. In recent years, as the degree of integration in integrated circuits increases, it has been requested to form an ultra fine pattern in the submicron region or the quarter micron region. With such a trend, an exposure wavelength tends to become shorter, for instance, from g-line to i-line and further to a KrF excimer laser beam.
Moreover, the development of lithography using an electron beam, an X ray or an EUV beam also proceeds at present in addition to the use of an excimer laser beam. In particular, the lithography using an EUV beam as the light source is regarded as the promising pattern formation technique of next generation or after the next generation, and the extensive investigations have been made. Performance required for the resist used includes high sensitivity, high resolution and good line edge roughness. However, since there is a trade off relation between the above-described performances, it is important how these performances are satisfied at the same time. The term “line edge roughness” as used herein means a phenomenon wherein an edge between a line pattern of resist and a surface of substrate irregularly fluctuates in the direction vertical to the line due to the characteristics of resist, and the edge looks uneven when the pattern is observed from just above. Since the unevenness is transferred to the substrate in an etching step using the resist as a mask, the unevenness causes deterioration in electric properties thereby resulting in the yield reduction. Particularly, in the ultra fine region of 0.25 μm or less, the line edge roughness is the extremely important problem to be improved. The problem is also important in the lithography using an X-ray or an electron beam.
Separately from the above requirement, since the exposure is conducted under vacuum in the case of using the light source, for example, an electron beam, an X ray or an EUV beam, a problem of outgassing becomes also important in which a low boiling point compound, for example, a solvent or a resist material decomposed with high energy vaporizes to contaminate the optical device. Various investigations with respect to reduction of the outgassing have been recently made and various attempts, for instance, to restrain the vaporization of a low molecular weight compound by providing a top coat layer (see, for example, European patent 1,480,078) or to add a radical trapping agent capable of inhibiting the decomposition of a polymer (see, for example, U.S. Pat. No. 6,680,157) have been made. On the other hand, means for reducing the outgassing regarding an acid generator has been desired.
Heretofore, as a resist suitable for the lithography process using an electron beam, an X ray or an EUV beam, a chemical amplification resist mainly utilizing an acid catalyst reaction has been used in view of high sensitivity. With respect to a positive resist, a chemical amplification resist composition containing as the main components, a phenolic polymer having a property of being insoluble or hardly soluble in an aqueous alkali solution and becoming soluble in the aqueous alkali solution upon the action of an acid and an acid generator has been investigated. However, in a conventional resist using a polymer compound as a material, there is a problem in that the molecular shape of the polymer compound is reflected in the pattern profile and line edge roughness.
On the other hand, in recent years, it has been proposed to use a low molecular weight compound from the stand point of miniaturization of pattern and low line edge roughness. For instance, resist compositions using a phenol compound derivative having a specific structure (see, for example, JP-A-10-120610 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-A-10-83073, JP-A-2000-305270 and JP-A-2003-183227), calixarene having a specific structure (see, for example, JP-A-10-120610 and JP-A-11-322656), calixresorcinolarene (see, for example, JP-A-11-322656 and JP-A-2003-321423), or a phenolic dendrimer including a mother skeleton of calixresorcinolarene (see, for example, JP-A-10-310545) are disclosed.
However, it is unable to satisfy the high sensitivity, high resolution and good line edge roughness at the same time in the ultra fine region only by means of using such a low molecular weight compound. Moreover, a sufficient investigation is still not made at present with respect to suppression of the outgassing which is an especially important performance required for the EUV lithography.